Method of fabricating fluidic plates and devices by irradiation of photopolymers

ABSTRACT

In general and in one preferred method, a diaphragm plate may be formed by providing a vessel containing a quantity of a light-transmittive first photopolymer compound which includes, as mixed constituents, a reactive oligomer resin, a reactive monomer diluent and a photoinitiator. A first unmasked surface of the compound is irradiated with ultraviolet (UV) light for solidifying the surface to a depth equal to the relief thickness, i.e., the desired diaphragm thickness. A second surface of the compound is irradiated with UV light subsequent to being covered with a opaque mask which defines the shape of the diaphragm. This irradiation completes the formation of the diaphragm plate by solidifying the remaining, unmasked quantity of compound. The unsolidified compound is then removed from the masked area of the plate. Other preferred methods are also disclosed.

This invention relates to the fabrication of structures by irradiatingphotopolymers. More particularly, it relates to such a method forpneumatic device plates, substantially unsupported structures useful ascontrol elements in otherwise conventional fluidic devices. The methodalso relates to the fabrication of free-standing fluidic control deviceswhich incorporate diaphragm plates having certain movable controlportions which cooperate with, for example, more rigid interface platesembodying nozzles, control orifices and the like.

The fabrication of certain structures using photopolymers has long beenknown. For example, U.S. Pat. Nos. 4,137,081; 4,174,218 and 4,228,232,and other patents cited therein contain certain teachings relative tothe fabrication of printing plates using disclosed polymers. That it ispossible to fabricate certain types of fluidic elements and circuitsusing photopolymer material is suggested in a publication entitled"Fluidics" which was published by Fluid Amplifier Associates of AnnArbor, Mich., the available portion of which is attached hereto asAppendix I. The publication is believed to have been made in the 1960's.However, the structures described and illustrated therein as well asprinting plates fabricated using the teachings of the aforementionedPatents use, as a starting material, a sheetlike substance frequentlydisposed upon rigid support materials. Further, an article in HIGHTECHNOLOGY magazine, issue of August 1983, includes certain teachingsregarding the use of lasers to form photopolymers and a copy of thatarticle is attached hereto as Appendix II.

While the aforementioned Patents and articles are reasonably definitiveof methods useful for fabricating fully relief plates as, for example,printing plates from a sheet material which is sensitive to ultraviolet(UV) light, they have failed to provide solutions to the fabrication ofsubstantially unsupported pneumatic device plates such as interfaceplates and diaphragm plates which are useful alone or in conjunctionwith one another in the art of fluidic control devices. While themethods described herein are broadly useful in the construction ofliquid and gaseous fluidic devices, they will be described in the fieldof pneumatics as being exemplary.

Pneumatic control devices frequently include, as a component thereof, athin, resilient and highly flexible diaphragm which serves at least twofunctions. The diaphragm may prevent the flow of air between twoadjacent chambers and/or may act as a flow controlling device forpreventing, metering or permitting full flow of air into or out of arigid control nozzle by movably reacting to minute changes indifferential pressure across the diaphragm. An example of an apparatuswhich uses such a diaphragm is shown and described in U.S. Pat. No.4,207,914. These functional requirements dictate that the diaphragm behighly resilient, have a smooth surface for nozzle closure and havesufficient strength to withstand pressures typically encountered in thepneumatic control system to which they are applied. For example, inknown heating, ventilating and air conditioning (HVAC) pneumatic controlsystems, pressures of 20-25 psig are usually encountered. Conventionaldiaphragms are fabricated of rubber, neoprene or Buna N in flat sheetform or are molded to include ribs and peripheral sealing shoulders. Theuse of diaphragms of this type is frequently attended by the use ofmultiple clamping screws and reinforcing plates to help maintainair-tight integrity and by the use of adhesives which often undesirablytend to flow to unwanted areas, thereby impairing the performancequality of the finished structure.

Diaphragms of the conventional type are frequently mounted adjacentinterface plates which include, for example, control orifices havingdiameters on the order of a few thousandths of an inch and controlnozzles, the ported tips of which interact with the diaphragm surface.Unlike the diaphragms, these interface plates must be relatively rigidand capable of being molded or otherwise fabricated to close dimensionaltolerances and with smooth surfaces including smooth orifice passages.Prior to the method of the instant invention, conventionally fabricatedpneumatic control devices were characterized by the inclusion of supportplates, covers, gasket rings, clamping clips and assembly screwsrequired to form the complete apparatus. A method of fabricating adiaphragm plate, an interface plate and a free-standing fluidic controldevice, all by irradiating photopolymers and which results in a dramaticreduction in required time and in the number of parts comprising anassembly and therefore, in manufactured costs would be a distinctadvance in the arts.

SUMMARY OF THE INVENTION

In general and in one preferred method, a diaphragm plate may be formedby providing a vessel containing a quantity of a light-transmittivefirst photopolymer compound which includes, as mixed constituents, areactive oligomer resin, a reactive monomer diluent and aphotoinitiator. A first unmasked surface of the compound is irradiatedwith ultraviolet (UV) light for solidifying the surface to a depth equalto the relief thickness, i.e., the desired diaphragm thickness. A secondsurface of the compound is irradiated with UV light subsequent to beingcovered with a opaque mask which defines the shape of the diaphragm.This irradiation completes the formation of the diaphragm plate bysolidifying the remaining, unmasked quantity of compound. Theunsolidified compound is then removed from the masked area of the plate.

In another preferred method, irradiation of the first, unmasked surfacemay be omitted and the second surface is irradiated subsequent to beingcovered with a mask having areas of different opacities, theconfiguration and the opacity of each area being selected to define, forexample, a flow channel, a diaphragm or a control passage when thesecond surface is uniformly irradiated with collimated UV light.

In yet another preferred method, a vessel is provided which contains aquantity of a light transmittive first photopolymer compound for formingthe diaphragm portion of a diaphragm plate. The quantity of the firstcompound is selected to provide a first depth equal to the desiredthickness of the diaphragm portion. After solidifying the first compoundby irradiation with UV light, a quantity of a second compound is castatop the first compound with the combined depths of the first and secondcompounds being equal to the desired thickness of the diaphragm plate. Asurface of the second compound is partially covered by an opaque maskdefining a diaphragm shape and irradiation of the second compound willform the diaphragm plate by solidifying the unmasked quantity of thesecond compound, thereby bonding it to the first compound.

A free-standing fluidic control device may be fabricated by using atleast one diaphragm plate and by further providing a plurality ofvessels, each containing a quantity of a light-transmittive secondphotopolymer compound for forming an interface plate. Each quantity hasa first surface which is partially covered by an opaque mask defining atleast one control channel and at least one control nozzle. These firstsurfaces are irradiated with UV light to solidify the unmaskedquantities of the second compound, thereby forming a plurality ofinterface plates. The unsolidified compound is then removed from themasked areas of the plates and the plates are bonded one to another toform a free-standing pneumatic control device.

It is an object of the present invention to provide a method forfabricating pneumatic device plates such as a diaphragm plate usingphotopolymers.

Yet another object of the present invention is to provide a method forfabricating relatively rigid interface plates using photopolymers.

Still another object of the present invention is to provide a method forfabricating diaphragm and interface plates which may be bonded to oneanother by irradiation to form a free-standing pneumatic control device.

Yet another object of the present invention is to provide a method forfabricating diaphragm and interface plates by the use of masks havingareas of the same or different opacities.

Still another object of the present invention is to provide a method forfabricating diaphragm and interface plates by the use of diffuse orcollimated ultraviolet light.

Another object of the present invention is to provide a method forfabricating such plates which may have substantial thickness, on theorder of up to one-half inch. How these and other objects will beaccomplished will become more apparent from the detailed descriptionthereof taken in conjunction with the accompanying drawing.

DESCRIPTION OF THE DRAWING

FIG. 1 is a side elevation view in cross section of a vessel useful forcarrying out a method of the invention.

FIG. 2 is a top plan view of a lower plate used in the vessel of FIG. 1;

FIG. 3 is a top plan view of an exemplary mask useful in a method of theinvention;

FIG. 4 is a top plan view of a spacer plate useful in the vessel of FIG.1;

FIG. 5 is a top plan view of a top plate useful in the vessel of FIG. 1;

FIG. 6 is a side elevation view in cross-section of another vesseluseful in carrying out a method of the invention;

FIG. 7 is a top plan view of another exemplary mask useful in carryingout a method of the invention;

FIG. 7A is a cross sectional elevation view of a plate formed by the useof the mask of FIG. 7.

FIG. 8 is a top plan view of a bottom mask useful in fabricating aninterface plate according to a method of the invention;

FIG. 9 is a top plan view of a top mask useful in fabricating aninterface plate according to a method of the invention;

FIG. 10 is a top plan view of a mask useful in forming an interfaceplate according to a method of the invention;

FIG. 11 is a cross-sectional side elevation view of an interface plateformed using the mask of FIG. 10;

FIG. 12 is a cross-sectional side elevation view of a source ofcollimated ultraviolet light;

FIG. 13 is a simplified cross-sectional side elevation view of apneumatic pilot positioner having incorporated therewithin a diaphragmplate made in accordance with the invention, and;

FIG. 14 is a top plan view of the diaphragm plate useful in theapparatus of FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED METHODS

To form a perimeter-supportable diaphragm plate which has a movablediaphragm, it is preferable to use a vessel, a mask and a first compoundto be irradiated and one preferred vessel 10 will be first described.Referring to FIGS. 1 through 5 inclusive, and especially to FIG. 1, asuitable vessel 10 may be formed by using, in the order of assembly frombottom to top, a lower plate 11, a spacer plate 13, and a top plate 15.Referring particularly to FIG. 2, the rigid lower plate 11 has a topsurface 17 and a bottom surface parallel thereto and includes aperimeter portion 19 which may be conveniently formed of metal tosurround and secure a central window 21, preferably formed of quartz,soda lime glass or other rigid material transmittive of UV light. Foroptimum quality of the diaphragm plate to be formed, the plate 11 andthe window 21 will have co-planar surfaces. The plate 11 also includes aplurality of upwardly vertically projecting, cylindrical locating dowels23 for vertically aligning the plates 11, 13, 15 and masks duringassembly. The spacer plate 13 of FIG. 4 has a thickness determinative ofthe thickness of the diaphragm or interface plate to be fabricated andis likewise preferably rigidly made of metal, has parallel top andbottom surfaces and has formed therein a central aperture 25 having ashape and location generally coincident with that of the window 21. Theplate 13 further includes a plurality of dowel holes 27 sized andlocated to receive the dowels 23 with closely-fitted, sliding fit. Thelocations of the dowels 23 and dowel holes 27 are selected to verticallyalign the window 21 and the aperture 25. The spacer plate 13 includes,on its upper surface, a pair of runner channels 29, one each in fluidflow communication with a fill port 31 and with an overflow port 33. Thefill port 31 and its related channel 29 may be used for flowingphotopolymer into the vessel cavity 35 as described below while therunner channel 29 and its related port 33 will permit displaced air tobe expelled from the cavity 35. The volume of fluid contained within theports 31, 33 and channels 29 will provide makeup fluid required becauseof slight shrinkage of the volume of photopolymer contained within thecavity 35.

Referring further to FIG. 5, the top plate 15 with its incorporatedwindow 37 is closely similar in configuration to the bottom plate 11except that in place of the locating dowels 23, the top plate includesholes 39 for receiving those dowels 23 with close, sliding fit. The topplate 15 also includes a pair of holes, 41 and 43 to be in registry withthe ports 31 and 33 respectively when the top plate 15 is in position.All plates 11, 13, 15 include a plurality of through holes (not shown)arranged to be in registry one with another when the plates 11, 13, 15and mask(s) are assembled, the holes being sized to receive clampingbolts therethrough for maintaining the structural and air-tightintegrity of the vessel 10 while the vessel cavity 35 is being filledand while the photopolymer is being cured.

Referring next to FIG. 6, another preferred vessel 45 may be formedusing a lower plate 47, a spacer plate 49 and a top plate 51. Thoseplate surfaces which are horizontally disposed in FIG. 6 are preferablyformed to be parallel, smooth and flat in order to achieve the highestquality of the diaphragm plate or interface plate to be fabricated. Thelower plate 47 is preferably made of Teflon for easy vessel disassemblysince it has been found that with the UV light energy levels employed inthe invention, that portion of the photopolymer which is within a fewthousandths of an inch of the lower plate 47 will remain soft,permitting easy disassembly. The top plate 51 may be formed of soda-limeglass, with or without an image-bearing photoemulsion coating. If a topplate 51 is employed which has no such coating, a mask may be employedand placed atop the top plate 51. However, it has been found that whenthe image is disposed between the spacer plate 49 and the top plate 51,either in the form of a coating upon the underside of the top plate 51or in the form of a separate mask sheet, the quality of the photopolymerproduct formed by the method is improved.

The bottom plate 47 also includes a fill spigot 53 and an overflowspigot 55 formed therein, each spigot 53, 55 having its internal end influid flow communication with the cavity 57 defined by the bottom plate47, the spacer 49 and the top plate 51. Each spigot 53, 55 includes aneck portion 59, the vertical height of which is selected so that theupper terminus is disposed above the upper surface of the photopolymerproduct to be formed. The bottom plate 47, spacer 49, top plate 51 andany mask(s) 60 used therewith may be held in relative position one tothe other by a suitably configured clamping fixture (not shown).Clamping and unclamping will be facilitated if the fixture is of a typehaving a piston powered movable platen operated by compressed air.Liquid photopolymer may be placed into the cavity 57 by pressureinjection through the fill spigot 53 or by submersing the terminus ofthe fill spigot 53 in the polymer and drawing a slight vacuum at theoverflow spigot 55. In either event, the necks 59 of the spigots 53, 55should be filled with photopolymer so that fluid makeup caused by slightshrinkage may be effected.

With modifications, the vessel 45 of FIG. 6 may be used to carry out amethod for forming a diaphragm plate and is constructed to include afirst spacer 49 which has a thickness equal to the desired thickness ofthe diaphragm portion of such a plate, typically on the order of 5 mils.After filling the cavity 57 defined by the bottom plate 47, the firstspacer plate 49 and the top plate 51 with a first compound, thatquantity of compound is solidified by irradiation with UV light.Thereafter, the first spacer plate 49 is removed and a second spacerplate (not shown) is substituted therefor, the second spacer platehaving a thickness equal to the desired thickness of the diaphragmplate, i.e., greater than the thickness of the diaphragm portion alone.It will be observed that upon separation of the plate 49 from plate 51,the solidified first compound will adhere to the underside of thelatter. A quantity of a second compound is then cast within the secondspacer plate, i.e., beneath the solidified first compound, to a seconddepth, the first depth and the second depth, combined, being equal tothe thickness of the second spacer plate, i.e., the desired thickness ofthe completed diaphragm plate. As described below, the top surface ofthe second compound is then partially covered by an opaque mask whichdefines the desired diaphragm shape and location The assembly is againirradiated with ultraviolet light until solidification of the unmaskedportion occurs, thereby forming the complete diaphragm plate. It will beapparent from the foregoing that substitution of the first spacer plate49 with a second spacer plate may be avoided simply by providing asecond spacer plate which has a thickness equal to the desired depth ofthe second compound. In that instance, the two spacer plates would beused together when casting and solidifying the quantity of secondcompound. It will also be appreciated that the diaphragm plate so formedwill have two layers tightly bonded one to another, the firstincorporating the resilient diaphragm portion itself and the second,harder layer defining the diaphragm support structure.

Masks which may be useful in fabricating a diaphragm plate and afree-standing fluidic control device will now be described and it is tobe appreciated that the masks described below represent only a few ofthe thousands of mask configurations which might be employed. They areexemplary and the configuration of any mask which may be used with theinventive method is limited only by the parameters of the applicationand the imagination of the user after appreciating the teachings of thedisclosure.

Masks may be formed using a clear, sheet material as, for example,cellulose acetate and will have a preferred thickness of between 4 milsand 7 mils. The material should be capable of transmitting UV lighttherethrough without significant attenuation and should be chemicallyinert to such light to avoid discoloration or clouding which wouldotherwise impair light transmission. Two mask materials which have beenfound particularly useful are available from Eastman Kodak Company undertheir trademark Estar, film materials LPD 7 and LPF 7, both of which areof 7 mil thickness. A mask including an opaque negative portion isapplied, the opaque portion to have a size and shape corresponding withthose areas of the volume of fluid photopolymer where it is desired toprohibit curing by preventing UV light from striking the fluid. Allmask(s) to be used with the vessel 10 of FIG. 1, e.g. mask(s) 60, willpreferably have dowel receiving holes 62 and bolt throughholes to permitaligned incorporation of the mask into the completed assembly. Anexample of a mask 61 useful in the fabrication of a simple diaphragm isshown in FIG. 3 while an example of a second mask 63 useful forfabricating a compound, reinforced diaphragm is illustrated in FIG. 7.FIGS. 8 and 9 illustrate, respectively, a bottom mask 65 and a top mask67 useful for fabricating an interface plate which includes a pluralityof control nozzles and orifices. The manner of using these masks 65, 67will be set forth in greater detail following and it is to be noted thatany mask used as a top mask, e.g. mask 67, is to have holes 69therethrough which are in registry with holes 41 and 43 and with theports 31 and 33 to permit the free flow of the liquid photopolymer intoand out of the vessel cavity 35.

FIG. 10 illustrates another type of mask 71 which may be used to formdiaphragm plates or interface plates. It is to be appreciated that theillustrated mask 71 is merely by way of example and that the number andconfiguration of masks which may be employed after appreciating theteachings of the disclosure is very large. When employing a mask 71 ofthe type shown in FIG. 10, it is contemplated that the photopolymerproduct may be formed by irradiating only one surface thereof, i.e.,that surface in contact with or closest to the mask 71. The use of amask 71 of the type of FIG. 10 contemplates that the entirety of thevolume of compound confined within a vessel cavity 35 or 57 will beirradiated with UV light of the same intensity and for the same timeduration. In the exemplary FIG. 10 and as best seen in FIG. 11, thedepth of the pneumatic flow passage 73, the depth of the area 75 belowthe flexible diaphragm 77 and the presence and site of a through passage79 will be controlled by the location and relative opacity of each areaconfigured upon the mask 71. More specifically, the translucent maskmaterial 81 will have a first area 83 of a first exemplary opacity of100% which may be used for defining an orifice, a second circular area85 of a second exemplary opacity of 90% for defining the diaphragm 77and a third area 87 of an exemplary third opacity of 50% for definingthe flow passage 73.

The methods of the invention contemplate the use of a first compound forfabricating a simple diaphragm plate or the use of first and/or secondcompounds for fabricating a complex diaphragm plate or for fabricatingan interface plate. A suitable first compound is available from HerculesIncorporated of Wilmington, Del. as its formulation FF090. While theprecise formulation of this compound is not available from themanufacturer, it is a liquid which crosslinks in a chain reaction toform a relatively insoluble solid upon exposure to UV light. Thisreaction may terminate when cross linking of the compound becomes fullycomplete or when the cross linked material becomes opaque and therebyinhibits further linking.

It is believed that the FF090 compound probably has a close similarityto a chemical compound such as one containing a reactive oligomer resinhaving the following formula, a prepared polymer: ##STR1## a reactivemonomer diluent having either the formula ##STR2## or possibly both anda photoinitiator having a formula ##STR3## It is possible that the FF090compound also contains an inhibitor which prevents cross-linking whenexposed to ambient temperature and light conditions.

Those characteristics of the first compound which make it desirable inthe inventive method include a viscosity of about 50,000 cps in orderthat the compound be readily flowable into the vessel cavity 35 or 57.It should be capable of transmitting UV radiation in compoundthicknesses of up to approximately one-half inch since thicknesses ofthis order may be used in the formation of free standing fluidicdevices. The wavelength of UV light of which the compound should betransmittive has a range of 300-400 nm and a range of 350-380 nm ispreferred for making plates and devices. As an example of a firstcompound having acceptable transmittance, the FF090 material in a sampleof 0.080" thickness, transmitted the following power levels of UV lightto an underlying radiometer: 1.1 mw per sq. cm. upon initial exposure,0.81 mw per sq. cm. after 1 minute, 0.5 mw per sq. cm. after 2 minutes,0.4 mw per sq. cm. after 3 minutes, 0.33 mw per sq. cm. after 4 minutesand negligible amounts after 5 minutes. The exposure unit light sourceused for this test is described in detail below.

Additionally, a preferred first compound should be insensitive to andretain its fluid characteristic at room ambient temperatures andlighting levels. It should have low toxicity to be readily disposablewhen liquid, noncured compound is removed from the plates and shouldalso be able to provide sharp images when used with masks having opaqueportions as prior described. That is, it should have negligible UV lightself-propagating characteristics and substantially no tendency for curedportions to promote curing of adjacent material. A suitable firstcompound should also have a low shrinkage rate, at least less than about5% and preferably about 1% or less. Further, the compound should be ofthe thermoset type, i.e., it will not soften upon exposure to elevatedtemperatures as may be encountered in the application of the finishedplate or device. It should also be resistent to those chemicalsincluding oils as may be encountered in the application. As an example,plates and devices used in an HVAC system should be impervious tocompressor lubricating oil, some small quantity of which is almostinvariably entrained in the pneumatic fluid. It should also maintain itsresilience at those temperatures encountered in the application and inan HVAC system, such temperatures may approach the freezing point ofwater. A first compound useful for the construction of diaphragm plateswhich include a resilient, movable diaphragm such as diaphragm 77 as acontrol element portion thereof will preferably have a cured-statetensile strength in the range of 3500/4500 psi, elongation in the rangeof 55/70%, a Young's modulus in the range of 10,000/11,000 psi and ahardness in the range of 92/95 Shore A. It should be further capable ofresulting in a diaphragm which is able to undergo a fatigue test ofabout one million cycles at a peak pressure to be encountered in thesystem, nominally 20-25 psig in an HVAC system. Another substance usefulas a first compound is formula 2296 of Beacon Chemical Co. It isbelieved to be generally similar in chemical composition to the firstcompound described above.

When fabricating a compound diaphragm plate or an interface plate whichincludes control orifices and/or control nozzles, it is preferred thatsuch plates have greater rigidity than diaphragm plates. Accordingly, asecond compound is preferably used for fabrication of plates of theinterface type. The second compound is preferably a liquid in thenon-irradiated state which solidifies by cross-linking upon exposure toUV light. A preferred second compound has, as mixed constituents, afirst constituent of the first compound, a second constituent of a resinhaving a polyester base, at least two urethane groups, at least twomethacrylate monomers and a photoinitiator. A suitable secondconstituent photopolymer compound is available from Northwest ChemicalCo. under its formulation no. 5534. A third constituent of the secondcompound is preferably similar to the first compound but is formulatedwith a lower percentage of oligomer resin and higher percentages of themonomer diluent and the photoinitiator. This third constituent isavailable from Hercules Inc. under its formulation no. FF090-3. Thefourth constituent of the second compound comprises a lighttransmittive, fumed pyrogenic silica and a satisfactory fourthconstituent is available from Cabot Corporation of Boston, Mass. underits trade name Cab-O-Sil, M grade. Photocopies of three brochuresdescribing Cab-O-Sil pyrogenic silica are attached hereto as AppendicesIII, IV and V.

A preferred, fully cured second compound will have a tensile strength inthe range of 2800/3300 psi, an elongation in the range of 10-14% and aYoung's modulus in the range of 210,000/248,000 psi. The preferredsecond compound includes 20% to 40% of the first constituent, 60% to 80%of the second constituent, 0.25% to 5.0% of the third constituent and0.25% to 5.0% of the fourth constituent, all percentages by weight.Within the stated ranges, a preferred second compound will have 24%,75%, 0.5% and 0.5% of the first through fourth constituentsrespectively.

The preferred methods of using the aforedescribed vessels 10 or 45,masks and compounds to fabricate diaphragm plates and interface plateswill now be described. Referring to FIGS. 1-5 and if it is desired tofabricate a simple diaphragm plate, the bottom plate 11, bottom mask 61,spacer plate 13, top mask 60 and top plate 15 will be assembled in thatorder from bottom to top as generally shown in FIG. 1. A clear top mask60 having no negative (opaque portion) thereon is interposed between thespacer plate 13 and the top plate 15 for providing a smooth, fluidsealing surface. After assembly of the vessel 10 and installation of theretentive throughbolts, the first compound may be hypodermicallyinjected into the cavity 35 using the port 31 and associated runnerchannel 29 for the purpose. Injection continues until the level of thecompound is flush with the top of the overflow port 33. In order topermit the quantity of fluid within the fill port 31, overflow port 33and channels 29 to make up for shrinkage, the ports 31, 33 are thenmasked with small pieces of opaque tape for preventing the passage of UVlight therethrough.

To perform one or two-side irradiation, the commercially availableHercules Merigraph Type 35 exposure unit (not shown) has been found tobe suitable. Such a unit includes a rigid, light transmittive table forsupporting the vessel 10 and a first group of eight tubular, UV lampsarranged thereabove with the longitudinal axes of the lamps parallel oneto another and in a manner such that these axes define a plane parallelto the table. The lower surfaces of the lamp tubes are preferably spacedapproximately three inches above the top surface of the cavity 35defined within the vessel 10. Toshiba type 207FRL205 BL/M-A lamps havebeen found satisfactory for the purpose. The unit also includes anidentical bank of lamps disposed about 3-4 inches below the table andparallel thereto. When forming an exemplary diaphragm plate having athickness of about 0.055 inches, the upper bank of lamps is energizedfor about 3 seconds to irradiate the first unmasked upper surface,thereby solidifying it to a depth equal to the desired thickness of thediaphragm. In the example, an irradiation time of 3 seconds resulted ina diaphragm or relief thickness of about 0.005 inches. Following, thesecond bank of lamps is energized to irradiate the second, partiallymasked lower surface for the time required to solidify the remainingunmasked quantity of the first compound. It is to be appreciated thatthe volume of fluid confined between the relief thickness and the maskhaving the negative thereon will remain fluid during the aforementionedirradiation. The vessel is then disassembled and the unsolidified fluidis washed from the plate using a slightly alkali soap solution. It willbe noted that those surfaces of the resulting diaphragm plate which havebeen in contact with the bottom and top masks 61, 60 or plates 11, 15,as the case may be, will be slightly tacky to the touch. This isbelieved to arise from the presence of oxygen molecules in air whichresults in some inhibition of surface curing. If the plate is to be usedmerely as a component of an otherwise conventional fluidic device, thistacky material may be eliminated by a 5 to 10 minute postcure exposureto UV light in accordance with the following procedure. The plate issubmerged in a small amount of a solution prepared by dissolving 165grams of Post EX-1 powder in one gallon water. Post EX-1, commerciallyavailable from Hercules Inc., is essentially potassium persulfate. Thecontainer with the photopolymer plate and the potassium persulfatesolution is placed into the Merigraph exposure unit drawer, locatedabout 3 inches below the lower bank of ultraviolet lamps, where the 5minute to 10 minute post cure is accomplished. After the post cureirradiation from the lower bank of UV lamps, the plate is rinsed inwater. When the aforementioned second photopolymer compound is used forthe fabrication of a plate having greater rigidity, the post cure isaccomplished in air by placing the plate on the table of the exposureunit and simultaneously irradiating the plate using both the upper andlower banks of UV lamps for from 5 minutes to 10 minutes. On the otherhand, if the plate is to be used to form a free standing fluidic devicecomprised entirely of plates made of photopolymers, the tacky materialshould be retained for enhanced bonding characteristics. It should beappreciated that the foregoing is merely by way of example and not oflimitation and diaphragm plates having diaphragms of thicknesses up toabout 0.025 inches have been found useful in smaller pneumatic devices.

If it is desired to fabricate diaphragm plates or interface plates usingone or more masks having plural opacities as shown in FIG. 10, one mayuse a collimated light source 89 to irradiate only one side of thephotopolymer to be cured. As used in this specification, collimatedlight is defined to be light having rays maintained within about 3-4degrees of parallelism. A suitable source 89 of collimated UV light isshown in FIG. 12 to include a source 91 of light such as a mercury lampwhich has a peak output of about 365 nm wavelength. An irradiator 93 iscentrally positioned above the source 91 in a spaced apart relationthereto and includes an interior, generally hemispherical, highlypolished reflector surface 95. The source 89 also includes a generallysquare collimating tube 97 centrally disposed below the lamp 91 and theirradiator 93 in a spaced apart relation. The tube 97 includes an entryend having an aperture 99 therethrough of a diameter selected asdescribed below. The interior of the tube 97 is coated to be dead blackand has an exit end 101 to be spaced slightly above the surface to beirradiated. The length of the tube 97 and the diameter of the aperture99 are preferably selected in view of the maximum width W of the surfaceto be irradiated. That is, the selection of those dimensional parametersshould preferably be made so the maximum included angle 103 between alight ray 105 from the edge of the lamp 91 to the edge of the end 101and a reflected light ray 107 from the edge of the aperture 99 to theouter extremity of the surface be no more than about 1.6 degrees. When acollimated source 89 of the type described above is used for singlesided exposure, it will permit close dimensional control of thoseportions of the plates which lie vertically beneath or above the masksuch as mask 71.

If it is desired to fabricate a diaphragm plate wherein the diaphragmhas a diameter several times greater than the thickness of the parent,supporting plate, it has been found useful to fabricate the diaphragm asa compound structure, i.e., in a manner to have a central reinforcedarea. Accordingly, and referring to FIG. 7, a mask as shown in thatFIGURE will be interposed between the bottom plate 11 and the spacerplate 13 while a clear top mask will be used between the spacer plate 13and the top plate 15. Irradiation, vessel disassembly and washing in thetwo-sided manner described above will result in a partially completeddiaphragm plate, the cross section of which is shown in FIG. 7A. Thatis, it will have an outer, annular diaphragm area 107 and an annular,upward projecting shoulder 109 defining a pocket 111 therewithin. Thepocket 111 is preferably filled with the second compound to the level ofthe top rim of the shoulder 109 and the second compound is thereuponirradiated with UV light until solidified. With respect to eitherdiaphragm formed as described above, the slightly diffuse nature of thelight emanating from the exposure unit and the characteristics of thecompounds themselves will result in a diaphragm plate, either simple orcompound, having slightly rounded corners 113 which are resistive totearing during diaphragm flexure.

To fabricate an exemplary interface plate, reference is made to FIGS. 1,8 and 9. The mask 65 of FIG. 8 is interposed between the bottom plate 11and the spacer plate 13 while the mask 67 of FIG. 9 is interposedbetween the spacer plate 13 and the top plate 15. It will be noted thatthe mask 65 includes a plurality of configurations having opaque areas115 resembling the letter "Q" in shape and other opaque areas comprisingcircular dots 117. It will also be noted that the mask 67 of FIG. 9includes a plurality of circular dots 117 sized and located to be inregistry with those dots 117 of mask 65. When irradiated in the mannerdescribed above, and washed, the resulting interface plate will have aplurality of upwardly proJecting control nozzles, eight in the example,surrounded by grooves resembling trepan grooves which connect topassages through which pneumatic fluid may flow. The quantity ofcompound confined between the dots 117 appearing on the masks 65 and 67will remain liquid throughout the irradiation steps and when washed fromthe plate, will result in smooth sided, generally cylindrical shapedorifices through the plate. When fabricating an exemplary interfaceplate to have control nozzles, it is preferable to use the secondcompound for increased rigidity and washing removal of the uncuredportions of this compound may be accomplished with ethyl alcohol. Afterunderstanding the teaching of the specification, it will be appreciatedthat vessel 45 may be used in a manner similar to that of vessel 10.While the latter may better lend itself to experimental or prototypework, the former may better lend itself to situations requiring morerapid production rates.

The technique used for bonding a plurality of plates to form a freestanding fluidic control device will next be described. With respect toeach plate to be bonded, a 250 mesh screen may be overlaid thereon, thescreen to have masking conforming to those surface areas of the platewhere it is desired to omit the application of the bonding resin. Theplate is supported to contact the under surface of the screen and asmall amount of bonding resin is bladed or squeegeed across the screenin a manner such that it is caused to pass through the screen at theunmasked area and deposit as small spots of liquid resin upon thesurface to be bonded. When the screen is removed and the plate permittedto stand for a short time, the resin will flow to a homogeneous coatingonly a few microns in thickness. It is to be noted that of two platesurfaces to be bonded to one another, only one of those surfaces needhave bonding resin applied thereto.

Subsequent to coating plate surfaces to be bonded, the plates arestacked upon a doweled bonding fixture constructed of a pair ofrelatively thick quartz or glass clamping plates for confining thestacked assembly therebetween. The plates are clamped one to anotherwith spring loaded screws which are tightened to the degree necessary toextrude air from between the surfaces to be bonded. The quartz or glassselected is to be transparent to UV light and sufficiently thick towithstand clamping force. A plate thickness of approximatelythree-eighths inch has been found to be suitable for devices havingsurface dimensions of approximately two inches square. The stackedassembly is then irradiated with UV light for a period of about 10minutes or until the bonding resin has solidified. The resulting devicewill be virtually homogeneous across the bonded sections and will besuitable for use as a free-standing fluidic control device, requiringonly the attachment of control connections and perhaps a simple supportbracket. The aforedescribed second compound has been found to be asuitable bonding resin or, more preferably, resin formula No. 5534 asavailable from Northwest Chemical Company may be used. The latter has alower viscosity than the second compound and therefore will flow morereadily through the screen.

FIG. 13 is a simplified cross-sectional view of a commercially availablepneumatic pilot positioner 119, Model D9502 as manufactured by JohnsonControls, Inc. of Milwaukee, Wis. It has been found that the rubbercoated fabric diaphragm 121 used therein may be replaced by thediaphragm plate 123 shown in FIG. 14. This diaphragm plate 123 has aplurality of holes 125 for receiving conventional assembly screws andfurther includes a plurality of diaphragms of either the compound type,diaphragm 127, or of the simple type, diaphragms 129, made according tothe inventive method. It has been found that such a diaphragm plateformed of a photopolymer is of high quality, inexpensive to fabricateand readily able to withstand the rigors of pneumatic service within thepositioner 119.

While only a few preferred methods have been shown and described herein,the invention is not intended to be limited thereby but only by thescope of the claims which follow.

We claim:
 1. A method for forming a perimeter-supportable diaphragmplate having a movable diaphragm and useful as a component of apneumatic control device, the method including the steps of:providing avessel containing a quantity of a light-transmittive first photopolymercompound for forming a diaphragm plate, said first compound including,as mixed constituents, a reactive oligomer resin, a reactive monomerdiluent and a photoinitiator; irradiating a first unmasked surface ofsaid compound with ultraviolet light for solidifying said first surfaceto a depth equal to the desired thickness of a diaphragm, saidultraviolet light having a wavelength in the range of 300-400 nm;irradiating a second surface of said compound with said ultravioletlight, said second surface being partially covered by an opaque maskdefining the shape of said diaphragm, said irradiating of said secondsurface thereby forming said diaphragm plate by solidifying the unmaskedquantity of said compound, and; removing the unsolidified compound fromthe masked area of said plate.
 2. The invention set forth in claim 1wherein said first surface is solidified to a depth not in excess of0.025 of an inch, thereby establishing the thickness of said diaphragm.3. The invention set forth in claim 2 wherein said ultraviolet light hasa wavelength in the range of 350-380 nm.
 4. A method for forming aperimeter-supportable diaphragm plate having a movable diaphragm anduseful as a component of a pneumatic control device, the methodincluding the steps of:providing a vessel containing a quantity of alight-transmittive first photopolymer compound for forming the diaphragmportion of a diaphragm plate, said first compound including, as mixedconstituents, a reactive oligomer resin, a reactive monomer diluent anda photoinitiator, said quantity of said first compound having a firstdepth equal to the desired thickness of said diaphragm portion;solidifying said first compound by irradiation with ultraviolet light;providing a quantity of a second, light-transmittive photopolymercompound, said quantity being cast atop said first compound to a seconddepth, said first depth and said second depth, combined, being equal tothe desired thickness of said diaphragm plate, and; irradiating asurface of said second compound with ultraviolet light, said surfacebeing partially covered by an opaque mask defining a diaphragm shape,said irradiation of said second compound thereby forming said diaphragmplate by solidifying the unmasked quantity of said second compound. 5.The invention set forth in claim 4 wherein said vessel includes a bottomplate, a top plate and a spacer plate separable from said bottom and topplates, said first compound being received in a vessel including a firstspacer plate having a thickness equal to said first depth, said secondcompound being received in said vessel including a second spacer platesubstituted for said first spacer plate, said second spacer plate havinga thickness equal to said desired thickness of said diaphragm plate. 6.The invention set forth in claim 4 wherein said vessel includes a bottomplate, a top plate and at least one spacer plate disposed intermediatesaid bottom and top plates, said first compound being received in avessel including a first spacer plate having a thickness equal to saidfirst depth, said second compound being received in said vessel whichfurther includes a second spacer plate disposed intermediate said firstplate and said second plate, the combined thicknesses of said first andsecond spacer plates being equal to the desired thickness of saiddiaphragm plate.
 7. The invention set forth in claim 5 wherein saidsecond solidified compound has a hardness greater than the hardness ofsaid first solidified compound.
 8. The invention set forth in claim 6wherein said second solidified compound has a hardness greater than thehardness of said first solidified compound.
 9. A method for forming aperimeter-supportable diaphragm plate having a rigid center, movablediaphragm and useful as a component of a pneumatic control device, themethod including the steps of:providing a vessel containing a quantityof a light-transmittive first photopolymer compound for forming adiaphragm plate, said first compound including, as mixed constituents, areactive oligomer resin, a reactive monomer diluent and aphotoinitiator; irradiating a first unmasked surface of said compoundwith ultraviolet light for solidifying said first surface to a depthequal to the desired thickness of a diaphragm, said ultraviolet lighthaving a wavelength in the range of 300-400 nm; irradiating a secondsurface of said compound with said ultraviolet light, said secondsurface being partially covered by an opaque mask having a circularcentral mask area and an annular mask ring concentric to said centralarea and spaced apart therefrom to define an unmasked annulustherebetween for forming a diaphragm pocket; said irradiating of saidsecond surface thereby solidifying the remaining, unmasked quantity ofsaid first compound; removing the unsolidified first compound from themasked areas of said second surface; filling said pocket with alight-transmittive second photopolymer compound, and; irradiating saidsecond compound with ultraviolet light until said second compound issolidified.
 10. A method for fabricating a freestanding fluidic controldevice by irradiating light-sensitive polymer and including the stepsof:providing a vessel containing a quantity of a light-transmittivefirst photopolymer compound for forming a diaphragm plate; irradiating afirst unmasked surface of said first compound with ultraviolet light forsolidifying said first surface to a depth equal to the desired thicknessof a diaphragm; irradiating a second surface of said first compound withultraviolet light, said second surface being partially covered by anopaque mask defining a diaphragm shape, said irradiating of said secondsurface thereby forming said diaphragm plate by solidifying theremaining unmasked quantity of said first compound; providing aplurality of vessels, each containing a quantity of a light-transmittivesecond photopolymer compound for forming an interface plate; each ofsaid quantities having a first surface partially covered by an opaquemask defining at least one control channel; irradiating each of saidfirst surfaces with ultraviolet light solidifying the unmaskedquantities of said second compound, thereby forming a plurality ofinterface plates; removing unsolidified compound from the masked areasof said plates, and; bonding said plates one to another to form afreestanding pneumatic control device.
 11. The invention set forth inclaim 10 wherein said first compound is a liquid having as mixedconstituents a reactive oligomer resin, a reactive monomer diluent and aphotoinitiator and wherein said first compound solidifies bycrosslinking upon exposure to ultraviolet light and said second compoundis a liquid having as mixed constituents a first constitutent of saidfirst compound; a second constituent of a resin having a polyester base,at least two urethane groups, at least two methacrylate monomers and aphotoinitiator; a third constituent including said oligomer resin in apercentage by volume lower than that of said first compound, furtherincluding said diluent in a percentage by volume higher than that ofsaid first compound, further including said photoinitiator in apercentage by volume higher than that of said first compound; and afourth constituent comprising a light-transmittive, pyrogenic silica.12. The invention set forth in claim 11 wherein said bonding stepincludes the steps of:removing unsolidified compound from the maskedareas of said plates; depositing a thin layer of a light sensitivepolymer bonding agent upon one of each pair of plate surfaces to bebonded one to the other; arranging said plates in a stack assembly todefine said freestanding device; clamping said assembly with a forcesufficient to extrude gaseous fluid from between said plate surfaces tobe bonded, and; irradiating said assembly with ultraviolet light forsolidifying said bonding agent.
 13. A method for forming an interfaceplate having a movable diaphragm, a fluid flow channel and a fluidorifice, the method including the steps of:providing a vessel containinga quantity of a light-transmittive first photopolymer compoundincluding, as mixed constituents, a reactive oligomer resin, a reactivemonomer diluent and a photoinitiator; overlaying a first surface of saidcompound with a mask having a translucent area, a first area of a firstopacity for defining said diaphragm, a second area of a second opacityfor defining said channel and a third area of a third opacity fordefining said orifice, and; irradiating said first surface withultraviolet light until that volume of said compound overlaid by saidtranslucent area is solidified.